South American countries vowed Wednesday to eliminate the mosquitoes spreading Zika, the virus blamed for brain damage in babies, after a US patient caught it by having sex.

With health authorities warning the mosquito-borne illness could infect up to four million people, ministers from 14 countries held emergency talks in Uruguay to plot their response to the growing crisis, with fears the virus could spread worldwide.

The country worst hit, Brazil, said it was sending more than 500,000 personnel out to clean up and advise people about the disease.

The health ministers gathered in Montevideo signed a declaration vowing to “design and execute education campaigns to control the carriers” of the virus.

The fever starts with a mosquito bite and normally causes little more than a fever and rash.

But scientists suspect that when it strikes a pregnant woman, it can cause her baby to be born with microcephaly, or an abnormally small head.

Organizers of the Rio Olympics in Brazil in August have insisted Zika will not disrupt the Games.

– Sexual transmission risk –

Authorities in Texas on Tuesday said they had confirmed a case of the virus being transmitted between humans by sexual contact.

Dallas County officials said a patient was infected following sexual contact with someone who caught Zika in Venezuela.

Health authorities in Ireland urged men to wear a condom during sex for one month after returning from a country affected by Zika.

But in Mexico, one health official said more information was needed about the link between Zika and sex.

“We have to take this very cautiously. We have to wait for more scientific evidence,” said Cuitlahuac Ruiz, director of epidemiology at the Mexican health ministry.

British and Canadian authorities said returning travellers will be barred from donating blood for a month and three weeks respectively, underlining growing fears worldwide.

The South American officials gathered on Wednesday were reluctant to quantify the risk of sexual transmission.

“If that is confirmed, it will give a new dimension to the problem,” said the head of the Pan American Health Organization, Carissa Etienne.

She said Zika was now present in 26 countries across the Americas.

“What worries the ministers is the speed with which Zika virus infections have spread,” she told reporters on the sidelines of the talks.

“Their response to this problem will be to fight against the mosquito that transmits the virus.”

Etienne said her organization provided $850,000 to help countries fight Zika but that 10 times that amount would be needed.

– Global Zika fears –

The World Health Organization has declared the spike in serious birth defects in South America an international emergency and launched a global Zika response unit.

Colombia, Ecuador, El Salvador, Jamaica and the US territory of Puerto Rico have all warned women not to get pregnant.

Health experts warn that Zika poses a massive threat to Asia.

Thailand confirmed that a man contracted the infection and Indonesia has also reported a domestic case — as has Cape Verde off northwest Africa.

The WHO warned European countries to act early to stop Zika spreading.

The European Centre for Disease Prevention and Control said the mosquito has “re-colonized” Madeira in Portugal and parts of southern Russia and Georgia in recent years after disappearing from the continent in the 20th century.

It has been spotted as far north as the Netherlands.

Indian drugs company Bharat Biotech said it was developing the world’s first Zika vaccine and was ready to test it on animals.

French pharmaceutical giant Sanofi earlier said it had begun researching a vaccine for Zika, for which there is currently no specific treatment.